Variable pitch sheave assembly for fan drive system

ABSTRACT

A fan drive arrangement and method is provided for facilitating the cooling of engine coolant flowing through a radiator and an engine. The fan drive arrangement includes a variable pitch sheave assembly which moves between a first high speed position and a second low speed position. Variable pitch sheave assembly is interconnected by first and second drive belts to first and second drive pulleys operatively connected to the crankshaft of the engine and by first and second fan belts to corresponding fan pulleys connected to a fan shaft of a fan. Variable pitch sheave assembly includes first and second drive belt receiving grooves for receiving corresponding drive belts therein and first and second fan belt grooves for receiving corresponding fan belts therein. The depths of the fan belt grooves and the drive belt grooves of the variable pitch sheave assembly are varied in response to the temperature of the engine coolant flowing through the radiator so as to vary the fan speed accordingly.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 09/904,265,filed Jul. 12, 2001 and entitled: “Air Flow Arrangement for GeneratorEnclosure,” and of U.S. Ser. No. 09/904,421, filed Jul. 12, 2001 andentitled: “Generator Structure Incorporating Multiple ElectricalGenerator Sets.”

FIELD OF THE INVENTION

This invention relates generally to engine-driven, electricalgenerators, and in particular, to a generator structure incorporating avariable pitch sheave arrangement for facilitating the cooling of aradiator of an engine-driven, electrical generator.

BACKGROUND AND SUMMARY OF THE INVENTION

Engine-driven, electrical generators are used in a wide variety ofapplications. Typically, such electrical generators utilize a singledriving engine directly coupled to a generator or alternator through acommon shaft. Upon actuation of the engine, the crankshaft thereofrotates the common shaft so as to drive the alternator which, in turn,generates electricity. It can be appreciated that since the engine andthe alternator are housed in a single enclosure, a significant amount ofheat is generated within the enclosure during operation of theelectrical generator.

Heretofore, in order to cool the components of a prior electricalgenerator, louvers were provided in the walls of the enclosure thereof.A fan, coupled to the crankshaft of the engine, rotates during operationof the electrical generator. The rotating fan draws air into theenclosure through the louvers in the walls and blows air over thecomponents of the electrical generator, including the engine, thealternator, and the radiator. In such a manner, it is intended that theair passing over the components of the electrical generator have acooling effect on the components during their operation such that thetemperatures of the components are maintained below safe operatinglimits.

While functional under certain conditions, air flow arrangements ofprior electrical generators have significant limitations. Typically, thefan used to cool the radiator is rotated at a predetermined, constantspeed. It can be appreciated that during start-up of the electricalgenerator, the temperature of the engine coolant flowing through theradiator is at a minimum. As such, it is unnecessary to rotate the fanat full speed in order to cool the engine coolant flowing through theradiator. As the engine of the electrical generator approaches fulloperating speed, the temperature of the engine coolant flowing throughthe radiator increases. Consequently, it becomes necessary for therotational speed of the engine fan to increase in order for the enginefan to adequately cool the engine coolant flowing through the radiator.As such, it is highly desirable to provide a fan drive structure whichprovides greater cooling of the radiator as the temperature of thecoolant flowing therethrough increases.

Therefore, it is a primary object and feature of the present inventionto provide a fan drive system for an electrical generator structurewhich improves the overall operating efficiency of the same.

It is a further object and feature of the present invention to provide afan drive system for an electrical generator structure which moreeconomically cools the radiator of the generator structure than priorfan drive systems.

It is a still further object and feature of the present invention toprovide a fan drive system for an electrical generator structure whichis simple to operate and inexpensive to implement.

In accordance with the present invention, a variable pitch drive sheaveis provided for interconnecting first and second fan pulleys operativelyconnected to a fan by a rotatable fan shaft and first and secondrotatable drive pulleys. The fan generates an air flow through aradiator to cool the temperature thereof. The variable pitch drivesheave assembly includes a shaft extending along an axis and havingfirst and second opposite ends. A first outer sheave member ispositioned adjacent the first end of the shaft and a second outer sheavemember is positioned adjacent the second end of the shaft. Anintermediate sheave member is positioned between the first and secondends of the shaft. A first movable sheave member is slidably supportedon the shaft between the first outer sheave member and the intermediatesheave member. The first movable sheave member and the outer sheavemember defining a first drive pulley groove therebetween for receiving afirst drive belt. The first movable sheave member and the intermediatesheave member define a first fan pulley groove therebetween forreceiving a first fan belt. The second movable sheave member is slidablysupported on the shaft between the second outer sheave member and theintermediate sheave member. The second movable sheave and the secondouter sheave member define a second drive pulley groove therebetween forreceiving a second drive belt. The second movable sheave member and theintermediate sheave member define a second fan pulley groovetherebetween for receiving a second fan belt. The first drive beltoperatively connects the first drive pulley groove and the first drivepulley. The second drive belt operatively connects the second drivepulley groove and the second drive pulley. The first fan beltoperatively connects the first fan pulley groove and the first fanpulley. The second fan belt operatively connects the second fan pulleygroove and the second fan pulley. As described, rotation of the firstand second drive pulleys is translated to the first and second fanpulleys.

The drive sheave assembly may include an actuator operatively connectedto the shaft for moving the first and second movable sheave membersbetween a first high speed position and a second low speed position. Thefirst and second drive pulley grooves have a first depth when the firstand second movable sheave members are in the high speed position and asecond depth with the first and second movable sheave members in the lowspeed position. The first depth of the first and second drive pulleys isgreater than the second depth of the first and second drive pulleys. Inaddition, the first and second fan pulley grooves have a first depthwhen the first and second movable sheave members are in the high speedposition and a second depth when the first and second movable sheavemembers are in the low speed position. The first depth of the first andsecond fan pulleys grooves is less than the second depth of the firstand second fan pulley grooves. It is contemplated to provide amonitoring device for monitoring the temperature of the radiator. Themonitoring device controls movement of the actuator in response to thetemperature of the radiator.

In accordance with a further aspect of the present invention, a fandrive arrangement is provided. The fan drive arrangement operativelyconnects a drive shaft to a fan mounted on a rotatable fan shaft. Thefan drive arrangement includes first and second fan pulleysinterconnected to the fan shaft. Each drive pulley has a groove thereinfor receiving a corresponding fan belt. First and second drive pulleysare interconnected to the drive shaft. Each fan pulley has a groovetherein for receiving a corresponding drive belt. A variable pitchsheave assembly is also provided. The variable pitch sheave assembly ismovable between a first high speed position and a second low speedposition and includes a rotatable sheave shaft having first and secondopposite ends. A first outer member is fixed to the first end of thesheave shaft and a second outer member is fixed to the second end of thesheave shaft. An intermediate member is fixed to the sheave shaftbetween the first and second ends thereof. A first slidable memberslides along the sheave shaft between the first outer member and theintermediate member. The first slidable member and the first outermember define a first drive pulley therebetween and the first slidablemember and intermediate member define a first fan groove therebetween. Asecond slidable member is slidable along the sheave shaft between theintermediate member and a second outer member. The second slidablemember and the second outer member define a second drive groovetherebetween and the second slidable member and the intermediate memberdefine a second fan groove therebetween. A first drive belt is seated inthe groove in the first drive pulley and in the first drive groove totranslate rotation of the first drive pulley to the variable pitchsheave assembly. A second drive belt is seated in the groove in thesecond drive pulley and the second drive groove to translate rotation ofthe second drive pulley to the variable pitch sheave assembly. A firstfan belt is seated in the first fan groove and the groove in the firstfan pulley to transfer rotation of the variable pitch sheave assembly tothe first fan pulley. A second fan belt is seated in the second fangroove and the groove in the second fan pulley to translate rotation ofthe variable pitch sheave assembly to the second fan pulley.

The first and second drive grooves have a first depth with the variablepitch sheave assembly in the high speed position and a second depth withthe variable speed pitch assembly in the low speed position. The firstdepth of the first and second drive grooves is greater than the seconddepth of the first and second drive fan grooves. The first and secondfan grooves also have a first depth with the variable pitch sheaveassembly in the high speed position and a second depth with the variablepitch sheave assembly in the low speed position. The first depth of thefirst and second fan grooves is less than the second depth of the firstand second fan grooves.

An actuator is operatively connected to the variable pitch sheaveassembly for moving the variable pitch sheave assembly between the highspeed position and a low speed position. A controller is operativelyconnected to the actuator. The controller monitors the temperature ofthe radiator and controls operation of the actuator in response to thetemperature monitored.

In accordance with a further aspect of the present invention, a methodis provided of cooling the engine coolant flowing through a radiator.The method includes the step of monitoring a temperature of coolantflowing through the radiator. A fan is positioned adjacent to theradiator and rotates at a predetermined speed. The speed of the fan isvaried in response to the temperature of the coolant.

The method includes the additional steps of supporting the fan on arotatable fan shaft and a driven pulley attached thereto. The driven fanpulley includes a groove formed therein. A drive pulley is alsoprovided. The drive pulley has a groove formed therein which has apredetermined depth. A fan belt is positioned about the groove of thedriven fan pulley and the groove of the drive pulley such that rotationof the drive pulley is translated to the fan pulley by the fan belt. Thestep of varying the speed of the fan includes the additional step ofvarying the depth of the groove in the drive pulley. The depth of thegroove in the drive pulley is decreased to increase the speed of the fanand the depth of the groove in the drive pulley is increased to decreasethe speed of the fan.

In accordance with a still further aspect of the present invention, afan drive arrangement is provided. The fan drive arrangement operativelyconnects a drive shaft to a fan mounted on a rotatable fan shaft. Thefan drive arrangement includes first and second fan pulleysinterconnected to the fan shaft. Each fan pulley has a groove thereinfor receiving a corresponding fan belt. First and second drive pulleysare interconnected to the drive shaft. Each drive pulley has a groovetherein for receiving a corresponding drive belt. A variable pitchsheave assembly is movable between a first high speed position and asecond low speed position. The variable pitch sheave assembly includesfirst and second drive belt grooves and first and second fan beltgrooves. The drive belt grooves have a first depth with variable pitchassembly in the high speed position and a second depth with the variablepitch assembly in the low speed position. The fan belt grooves have afirst depth with variable pitch assembly in the high speed position andthe second depth with the variable pitch sheave assembly in the lowspeed position. First and second drive belts are seated in correspondingdrive belt grooves in the variable pitch sheave assembly and incorresponding grooves in the drive pulleys to translate rotation of thedrive pulleys to the variable pitch sheave assembly. First and secondfan belts are seated in corresponding fan belt grooves in the variablepitch sheave assembly and in corresponding grooves in the fan pulleys totranslate rotation of the variable pitch sheave assembly to the fanpulleys.

The variable pitch sheave assembly of the fan drive arrangement includesa rotatable sheave shaft having first and second opposite ends. A firstouter member is affixed to the first end of the sheave shaft and asecond outer member is fixed to the second end of the sheave shaft. Anintermediate member is fixed to the sheave shaft between the first andsecond ends thereof. A first slidable member is slidable along thesheave shaft between the first outer member and the intermediate member.The first slidable member and the first outer member define the firstdrive belt groove therebetween. The first slidable member and theintermediate member define the first fan belt groove therebetween. Asecond slidable member is slidable along the sheave shaft between theintermediate member and the second outer member. The second slidablemember and the second outer member define the second drive groovetherebetween. The second slidable member and the intermediate memberdefine a second fan belt groove therebetween.

The first depth of a drive belt grooves is greater than the second depthof the drive belt grooves. On the other hand, the first depth of the fanbelt grooves is less than the second depth of the fan belt grooves. Anactuator is operatively connected to the variable pitch sheave assemblyfor moving the variable pitch sheave assembly between the high speedposition and the low speed position. A controller is operativelyconnected to the actuator and monitors the temperature of the radiator.The controller controls operation of the actuator in response to thetemperature of the radiator.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings furnished herewith illustrate a preferred construction ofthe present invention in which the above advantages and features areclearly disclosed as well as others which will be readily understoodfrom the following description of the illustrated embodiment.

In the drawings:

FIG. 1 is a side elevational view, with portions broken away, showing agenerator structure of the present invention;

FIG. 2 is a top plan view, with portions broken away, showing thegenerator structure of FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3—3 of FIG. 2;

FIG. 4 is a schematic view showing rotation of the drive shafts of eachgenerator set of the generator structure of FIG. 1;

FIG. 5 is a cross-sectional view taken along line 5—5 of FIG. 2;

FIG. 6 is a schematic view showing connection of the generator structureof FIG. 1;

FIG. 7 is an enlarged, cross-sectional view taken along line 7—7 of FIG.3;

FIG. 8 is a cross-sectional view taken along line 8—8 of FIG. 7;

FIG. 9 is an end view of a fan drive arrangement for the generatorstructure of the present invention;

FIG. 10 is a side elevational view of the fan drive arrangement of FIG.9;

FIG. 11 is an enlarged, end view of the fan drive arrangement of FIG. 9;

FIG. 12 is a cross-sectional view taken along line 12—12 of FIG. 9;

FIG. 13 is a cross-sectional view taken along line 13—13 of FIG. 11;

FIG. 14 is a cross-sectional view taken along line 14—14 of FIG. 12; and

FIG. 15 is a cross-sectional view taken along line 15—15 of FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a generator structure in accordance with thepresent invention is generally designated by the reference numeral 10.Generator structure 10 includes an enclosure 12 having first and secondsidewalls 14 and 16, respectively, interconnected by first and secondend walls 18 and 20, respectively, and a lower bottom support 22.Sidewalls 14 and 16 and end walls 18 and 20 define interior 24 ofenclosure 12 therebetween. Sidewalls 14 and 16 may include one or moredoors 25 therein for allowing a user access to interior 24 of enclosure12.

Referring to FIGS. 1 and 3, base 26 is mounted to the underside 22 a ofsupport 22 of enclosure 12 for supporting generator structure 10 above asupporting surface 28 such as the ground, a concrete slab or a mountingpad. Base 26 is generally rectangular in shape and defined by verticalsidewalls 30 and 32 interconnected by a bottom wall 34. Inner surfaces30 a and 32 a of sidewalls 30 and 32, respectively, and inner surface 34a of bottom wall 34 define cavity 36 in base 26. It is contemplated toprovide supports 38 and 40 adjacent outer surfaces 30 b and 32 b ofsidewalls 30 and 32, respectively, to stabilize base 26.

Generator structure 10 further includes a roof structure, generallydesignated by the reference numeral 42. Roof structure 42 includes anupper panel 44 having first and second openings 46 and 48, respectively,extending therethrough. Upper panel 44 has first and second sides 50 and52, respectively, which are generally parallel to sidewalls 14 and 16 ofenclosure 12. First and second side panels 54 and 56, respectively,extend from corresponding sides 50 and 52, respectively, of upper panel44 and diverge from each other. Side panel 54 terminates at a terminaledge 54 a which is laterally spaced from sidewall 14 of enclosure 12 soas to define a first inlet 57 therebetween. Similarly, side panel 56terminates at a terminal edge 56 a which is spaced from sidewall 16 ofenclosure 12 so as to define a second inlet 58 therebetween.

Separation panel 60 extends between inner surface 54 b of first sidepanel 54 of roof structure 42 and inner surface 56 b of second sidepanel 56 of roof structure 42. Separation panel 60 includes first andsecond portions 62 and 64, respectively, interconnected by a centralportion 66. Central portion 66 intersects upper panel 44 such that firstportion 62 of separation panel 60 and upper panel 44 define a firstattic chamber 68 therebetween in roof structure 42 and second portion 64of separation plate 60 and upper panel 44 define a second attic chamber70 therebetween in roof structure 42. It can be appreciated that firstattic chamber 68 in roof structure 42 may communicate with the ambientair outside of generator structure 10 through opening 46 in upper panel44. In addition, second attic chamber 70 in roof structure 42 maycommunicate with the ambient air outside of generator structure 10through second opening 48 in upper panel 44.

Separation panel 60 includes first end 60 a spaced from end wall 18 ofenclosure 12 so as to define first attic chamber inlet 72 betweensidewalls 14 and 16. First attic chamber inlet 72 allows for first atticchamber portion 68 in roof structure 42 to communicate with interior 24of enclosure 12 therethrough. Second end 60 b of separation panel 60 isspaced from end wall 20 of enclosure 12 so as to define second atticchamber inlet 74 between sidewalls 14 and 16, FIGS. 7-8. Second atticair inlet 74 allows for second attic chamber 70 in roof structure 42 tocommunicate with interior 24 of enclosure 12 therethrough.

Lower surface 60 c of separation panel 60 and the inner surfaces 54 band 56 b of side panels 54 and 56, respectively, of roof structure 42define an eave chamber 76 in roof structure 42. An outlet 78 to eavechamber 76 of roof structure 42 is provided between sidewalls 14 and 16of enclosure 12. It can be appreciated that interior 24 of enclosure 12may communicate with ambient air outside of generator structure 10through eave chamber 76 in roof structure 42 and through first andsecond inlets 57 and 58, respectively.

As best seen in FIG. 2, generator structure 10 includes first and secondgenerator sets 80 and 82, respectively, positioned next to one anotherwithin interior 24 of enclosure 12. Generator set 80 includes analternator end 80 a adjacent first end wall 18 of enclosure 12 and a fanend 80 b adjacent second end wall 20 of enclosure 12. Generator set 82includes a fan end 82 a adjacent first end wall 18 of enclosure 12 andan alternator end 82 b adjacent second end wall 20 of enclosure 12.

Generator set 80 includes an engine, generally designated by thereference numeral 84, which is supported on bottom support 22 ofenclosure 12. As is conventional, engine 84 receives fuel such asdiesel, natural gas or liquid propane vapor through an intake. The fuelis compressed and ignited within the cylinders of engine 84 so as togenerate reciprocating motion of the pistons of engine 84. Thisreciprocating motion of the pistons of the engine 84 is converted torotary motion such that engine 84 rotates a drive or crankshaft 85, FIG.4. Crankshaft 85 of engine 84 is coupled to alternator 86 such that ascrankshaft 85 is rotated by the operation of engine 84, crankshaft 85drives alternator 86 which, in turn, converts the mechanical energygenerated by engine 84 to electrical power for transmission anddistribution. Conduit 88 has a first end operatively connected toalternator 86 within connection box 90 and a second, opposite end.Conduit 88 carries the electrical power generated by first generator set80 to bus 89.

First generator set 80 further includes radiator 92 operativelyconnected to engine 84 such that engine coolant from engine 84circulates through radiator 92 during operation of engine 84. As isconventional, radiator 92 includes a plurality of radiator tubes (notshown) through which the engine coolant flows. As hereinafter described,it is intended that air within interior 24 of enclosure 12 pass over theplurality of radiator tubes of radiator 92 so as to effectuate a heatexchange between the engine coolant flowing through the plurality ofradiator tubes of radiator 92 and the air within enclosure 12.

In order to draw air over the plurality of radiator tubes of radiator92, generator set 80 includes a fan, generally designated by thereference numeral 96. Fan 96 includes a plurality of fan blades 98extending radially from central hub 100. Central hub 100 is rotatablysupported on a first side 92 a of radiator 92 by rotatable fan shaft102. Fan shaft 102 includes a driven wheel 104 extending radiallytherefrom. Driven wheel 104 is operatively connected to drive wheel 106through fan belts 108 and 110 and jack shaft 112. Drive wheel 106 isoperatively connected to crankshaft 85 of engine 84 such that drivewheel 106 is rotated by a crankshaft 85 during operation of engine 84.Rotation of drive wheel 106 is translated to driven wheel 104 throughbelts 108 and 110 and jack shaft 112 which, in turn, rotates fan 96.Rotation of fan 96 draws air through first and second inlets 57 and 58,respectively, in roof structure 42; across engine 84 of first generatorset 80; and across the plurality of radiator tubes of radiator 92 so asto cool engine 84 and the engine coolant flowing through the pluralityof radiator tubes of radiator 92. In addition, fan 96 urges the airdrawn across the plurality of radiator tubes of radiator 92 from theinterior 24 of enclosure 12 into second attic chamber 70 in roofstructure 42 through second attic chamber inlet 74; and out from roofstructure 42 through second opening 48 in upper panel 44.

The exhaust outlet of engine 84 of first generator set 80 isinterconnected to input 114 of muffler 116 through an exhaust pipe 118.Muffler 116 is positioned within second attic chamber 70 in roofstructure 42 such that the air urged by fan 96 from generator structure10 passes over muffler 116 to cool the same. Output of muffler 116 isoperatively connected to the input of exhaust discharge tube 120.Exhaust discharge tube 120 includes outlet end 122 which extends throughopening 48 in upper panel 44 of roof structure 42 and which communicateswith the ambient air outside generator structure 10.

Second generator set 82 includes an engine, generally designated by thereference numeral 124, which is supported on bottom support 22 ofenclosure 12. As is conventional, engine 124 receives fuel such asdiesel, natural gas or liquid propane vapor through an intake. It iscontemplated that engines 84 and 124 receive fuel from a common source.The fuel is compressed and ignited within the cylinders of engine 124 soas to generate reciprocating motion of the pistons of engine 124. Thisreciprocating motion of the pistons of engine 124 is converted to rotarymotion such that engine 124 rotates a drive or crankshaft 125.Crankshaft 125 of engine 124 is coupled to an alternator 126 such thatas crankshaft 125 is rotated by operation of engine 124, crankshaft 125drives alternator 126 which, in turn, converts the mechanical energygenerated by engine 124 to electrical power for transmission anddistribution. Conduit 128 has a first end operatively connected toalternator 126 within connection box 130 and a second opposite end.Conduit 128 carries the electrical power generated by second generatorset 82 to a bus 89, FIG. 6.

Second generator set further includes radiator 132 operatively connectedto engine 124 such that coolant from engine 124 circulates throughradiator 132 during operation of engine 124. As is conventional,radiator 132 includes a plurality of radiator tubes (not shown) throughwhich the engine coolant flows. As hereinafter described, it is intendedthat air within interior 24 of enclosure 12 pass over a plurality ofradiator tubes of radiator 132 so as to effectuate a heat exchangebetween the engine coolant flowing through the plurality of radiatortubes of radiator 132 and the air within enclosure 12.

In order to draw air over the plurality of radiator tubes of radiator132, generator set 82 includes a fan, generally designated by thereference numeral 134. Fan 134 includes a plurality of fan blades 136extending radially from central hub 138. Central hub 138 is rotatablysupported on a first side 132 a of radiator 132 by rotatable fan shaft140. Fan shaft 140 includes a driven wheel 142 extending radiallytherefrom. Driven wheel 142 is operatively connected to drive wheel 144through fan belts 146 and 148 and jack shaft 150. Drive wheel 144 isoperatively connected to crankshaft 125 of engine 124 such that drivewheel 144 is rotated by a crankshaft 125 during operation of engine 124.Rotation of drive wheel 144 is translated to driven wheel 142 throughbelts 146 and 148 and jack shaft 150 which, in turn, rotates fan 134.Rotation of fan 134 draws air through first and second inlets 57 and 58,respectively, in roof structure 42; across engine 124 of secondgenerator set 82; and through radiator 132 across the plurality ofradiator tubes thereof so as to cool engine 124 and the engine coolantflowing through the plurality of radiator tubes of radiator 132. Inaddition, fan 134 urges the air drawn across the plurality of radiatortubes of radiator 132 from the interior 24 of enclosure 12 into firstattic chamber 68 in roof structure 42 through first attic chamber inlet72; and out from roof structure 42 through first opening 46 in upperpanel 44.

The exhaust outlet of engine 124 of second generator set 82 isinterconnected to input 152 of muffler 154 through an exhaust pipe 156.Muffler 154 is positioned within first attic chamber 68 in roofstructure 42 such that the air urged by fan 134 from generator structure10 passes over muffler 154 to cool the same. Output of muffler 154 isoperatively connected to the input of exhaust discharge tube 158.Exhaust discharge tube 158 includes outlet end 160 which extends throughopening 46 in upper panel 44 of roof structure 42 and which communicateswith the ambient air outside generator structure 10.

Referring to FIG. 6, generator structure 10 includes system controller170 that is operatively connected to first and second generator sets 80and 82, respectively, through communication links 172 and 174,respectively. In addition, system controller 170 is operativelyconnected to transfer switch 176, for reasons hereinafter described, andto switches 178 and 180 in conduits 88 and 128, respectively.

Transfer switch 176 includes a first input operatively connected toutility source 182 and a second input electrically connected togenerator structure 10 through bus 89. The output of transfer switch 176is operatively connected to load 184. As is conventional, transferswitch 176 incorporates a switch which isolates the electrical powersupplied by utility source 182 and the electrical power supplied bygenerator structure 10 on bus 89. A monitoring circuit is operativelyconnected to utility source 182 to monitor the electrical power suppliedby utility source 182. In response to a power outage from utility source182, the monitoring circuit of transfer switch 176 advises systemcontroller 170 accordingly.

System controller 170 starts first and second generator sets 80 and 82,respectively, in a conventional manner and monitors the magnitude andphase of the electrical power generated thereby on conduits 88 and 128,respectively. Thereafter, system controller 170 adjusts the engine speedof engines 84 and 124 of first and second generator sets 80 and 82,respectively, via an electronic governor or the like such that the ACpower generated by first and second generators 80 and 82, respectively,is brought into alignment (synchronized) with each other such that thereis no phase difference between the sine waves and that the sine wavesare at the same frequency. In addition, system controller 170 regulatesthe output voltages of generator sets 80 and 82 in a conventional mannersuch that output voltages of generators sets 80 and 82 are generallyequal. System controller 170 closes switches 178 and 180 in conduits 188and 128, respectively, such that the combined AC power generated byfirst and second generator sets 80 and 82, respectively, is provided onbus 89. Transfer switch 176 automatically transfers load from utilitysource 182 to generator structure 10 such that generator structure 10provides AC power to load 184. Upon completion of the power outage, thetransfer switch automatically reconnects load 184 to the utility source182. In addition, the monitoring circuit of transfer switch 176 advisessystem controller 170 of generator structure 10 accordingly such thatsystem controller 170 terminates operation of first and second generatorsets 80 and 82, respectively.

As heretofore described, during operation of first and second generatorsets 80 and 82, respectively, engines 84 and 124 drive correspondingfans 96 and 134, respectively. Rotation of fan 96 draws air throughfirst and second inlets 57 and 58, respectively, in roof structure 42;across engine 84 of first generator set 80; and across the plurality ofradiator tubes of radiator 92 so as to cool engine 84 and the coolantflowing through the plurality radiator of radiator 92. Further, rotationof fan 96 urges the air drawn across the plurality of radiator tubes ofradiator 92 from the interior of enclosure 12 into second attic chamber70 in roof structure 42 through second attic chamber inlet 74. The airin second attic chamber 70 passes over muffler 116 positioned therein soas to cool the same. Thereafter, the air exits roof structure 42 throughsecond opening 48 in upper panel 44.

Similarly, rotation of fan 134 draws air through first and second inlets57 and 58, respectively, in roof structure 42; across engine 124 ofsecond generator set 82; and across the plurality of radiator tubes ofradiator 132 so as to cool engine 124 and the engine coolant flowingthrough the plurality of radiator tubes of radiator 132. In addition,fan 134 urges the air drawn across the plurality of radiator tubes ofradiator 132 from the interior 124 of enclosure 12 in first atticchamber 68 in roof structure 42 through first attic chamber inlet 72.The air in first attic chamber 68 passes over muffler 154 positionedtherein so as to cool the same. Thereafter, the air exits roof structure42 through first opening 46 in upper panel 44.

Referring to FIG. 9, an alternate fan drive arrangement is generallydesignated by the reference numeral 200. As hereinafter described, fandrive arrangement 200 is used to drive fan 134. However, it can beappreciated that a second fan drive arrangement (not shown), identicalin structure to fan drive arrangement 200, may be used to drive fan 96without deviating from the scope of the present invention.

As best seen in FIG. 10, jack shaft 150 is operatively connected todrive shaft 202 for rotational movement therewith. Drive pulleys 204 and206 project radially from drive shaft 202 and include correspondinggrooves therein for accommodating drive belts 208 and 210, respectively,therein. Drive belts 208 and 210 translate rotation of drive pulleys 204and 206, respectively, to variable pitch sheave assembly 212, ashereinafter described.

Referring to FIGS. 12-13, variable pitch sheave assembly 212 includes arotatable sheave shaft 214 extending along a longitudinal axis andhaving first and second opposite ends 216 and 218, respectively. Firstouter sheave member 220 projects radially from and is fixed to sheaveshaft 214 adjacent first end 216 thereof for rotational movement withsheave shaft 214. First outer sheave member 220 includes radially inneredge 222 engaging sheave shaft 214 and radially outer edge 224. Inneredge 222 and outer edge 224 of first outer sheave member 220 areinterconnected by an inwardly directed surface 226 having a disc-shaped,radially inner portion 226 a and a conical-shaped, radially outerportion 226 b.

Second outer sheave member 228 projects radially from and is fixed tosheave shaft 214 adjacent second end 218 thereof for rotational movementwith sheave shaft 214. Second outer sheave member 228 includes radiallyinner edge 230 engaging sheave shaft 214 and radially outer edge 232.Inner edge 230 and outer edge 232 of second outer sheave member 228 areinterconnected by an inwardly directed surface 234 having a disc-shaped,radially inner portion 234 a and a conical shaped, radially outerportion 234 b.

Intermediate sheave member 236, projects radially from and is fixed tosheave shaft 214 for rotational movement therewith at a locationequidistant from first and second ends 216 and 218, respectively, ofsheave shaft 214. Intermediate sheave member 236 includes radially inneredge 238 engaging sheave shaft 214 and radially outer edge 240. Inneredge 238 and outer edge 240 of intermediate sheave member 236 areinterconnected by first and second sides 242 and 244, respectively.First surface 242 of intermediate sheave member 236 is directed towardsfirst outer sheave member 220 and includes a disc-shaped, radially innerportion 242 a and a conical-shaped outer portion 242 b. Second side 244of intermediate sheave member 236 is directed towards second outersheave member 228 and includes a disc-shaped, radially inner portion 244a and a conical-shaped, radially outer portion 244 b.

First movable sheave member 246 is slidably mounted on sheave shaft 214and is movable between first outer sheave member 220 and intermediatesheave member 236. First movable sheave member 246 includes radiallyinner edge 248 which is slidable along sheave shaft 214 and radiallyouter edge 250. Inner edge 248 and outer edge 250 of first movablesheave member 246 are interconnected by first and second sides 252 and254, respectively. First side 252 directed towards the first outersheave member 220 and second side 254 of first movable sheave member 246is directed towards intermediate sheave member 236. First side 252 offirst movable sheave member 246 includes a first disc-shaped radiallyinner portion 252 a and a conical shaped radially outer portion 252 b.First side 252 of first movable sheave member 246 and inwardly directedsurface 226 of first outer sheave member 220 define a first drive beltreceiving groove 255, for reasons hereinafter described. Second side 254of first movable sheave member 246 includes disc-shaped radially innerportion 254 a and a conical shaped radially outer portion 254 b. Secondside 254 of first movable sheave member 246 and first side 242 ofintermediate sheave member 236 define a first fan belt receiving groove257 there between, for reasons hereinafter described.

Variable pitch sheave assembly 212 further includes second movablesheave member 258 slidably mounted on sheave shaft 214 betweenintermediate sheave member 236 and second outer sheave member 228.Second movable sheave member 258 includes radially inner edge 260slidable along sheave shaft 214 and radially outer edge 262. Inner edge260 and outer edge 262 of second movable sheave member 258 areinterconnected by first and second sides 264 and 266, respectively.First side 264 of second movable sheave member 258 includes adisc-shaped, radially inner portion 264 a and a conical shaped radiallyouter portion 264 b. First side 264 of second movable sheave member 258and second side 244 of intermediate sheave member 236 define a secondfan belt receiving groove 268 therebetween, for reasons hereinafterdescribed. Second side 266 of second movable sheave member 258 includesa disc-shaped, radially inner portion 266 a and a conical-shaped,radially outer portion 26 b. Second side 266 of second movable sheavemember 258 and inwardly directed surface 234 of second outer sheavemember 228 define the second drive belt receiving groove 270therebetween. As hereinafter described, first and second movable sheavemembers 246 and 258, respectively, are movable between a first highspeed position, FIG. 13, and a second low speed position, FIG. 12.

Sheave shaft 214 is rotatably supported by a support bracket 272extending from opposite ends 216 and 218, thereof. As best seen in FIGS.9, 11 and 14-15, support bracket 272 is pivotably connected to bracketelement 274, which, in turn, is pivotably connected to enclosure 12 ofgenerator structure 10 in any conventional manner. Bracket element 274is further connected to vertical support 276 projecting from base 26 ofgenerator structure 10 by spring 278, for reasons hereinafter described.

Support bracket 272 is also pivotably connected to terminal end 280 ofshaft 282 of an actuator 284. Cylinder housing 286 of actuator 284 ispivotably connected to vertical support 276. It can be appreciated thatshaft 282 of actuator 286 is movable between a first extended position,FIG. 9, wherein variable pitch sheave assembly 212 is positioned in thelow speed position by support bracket 272 and a second retractedposition, FIG. 11, wherein the variable pitch sheave assembly 212 ispositioned in the high speed positioned by support bracket 272. Spring278 biases bracket 274 and support bracket 272 toward vertical support276 so as to maintain tension on drive belts 208 and 210, and on fanbelts 300 and 304.

Controller 290 is operatively connected to actuator 284 by line 292 tocontrol movement of shaft 282 of actuator 284 between the extendedposition, FIG. 9, and the retracted position, FIG. 11. In addition,controller 90 is operatively connected by line 296 to temperature sensor294 positioned adjacent to or within radiator 132 such that the positionof shaft 282 of actuator 284 and hence, the position of variable pitchsheave assembly 212, is responsive to the temperature sensed bytemperature sensor 294.

Referring to FIGS. 10 and 12-13, variable pitch sheave assembly 212 isoperatively connected to drive pulleys 204 and 206 by drive belts 208and 210, respectively. Drive belt 208 is seated within the groove indrive pulley 204 and within drive belt receiving groove 255 of variablepitch assembly 212. Drive belt 210 is seated within the groove in drivepulley 206 and within second drive belt receiving groove 270 of variablepitch sheave assembly 212. As described, rotation of drive pulleys 204and 206 is translated to variable pitch sheave assembly 212 by drivebelts 208 and 210, respectively.

First fan belt 300 is seated within first fan belt receiving groove 257of variable pitch sheave assembly 212 and within a groove extendingabout first fan pulley 302 which projects radially from rotatable fanshaft 140. Second fan belt 304 is seated within second fan beltreceiving groove 268 of variable pitch sheave assembly 212 and within agroove extending about second fan pulley 306 which projects radiallyfrom fan shaft 140. As described, rotation of variable pitch sheaveassembly, as heretofore described, is translated to fan pulleys 302 and306 through corresponding fan belts 300 and 304, respectively. It can beappreciated that rotation of fan pulleys 302 and 306 is translated byfan shaft 140 to fan 134 which, in turn, draws air through radiator 132,as heretofore described.

During start-up of generator structure 10, as heretofore described,controller 290 positions shaft 282 of actuator 284 in the extendedposition, FIG. 9. With shaft 282 of actuator 284 in the extendedposition, variable pitch sheave assembly 212 is in the low speedposition, FIG. 12, wherein variable pitch sheave assembly 212 is closerto drive pulleys 204 and 206 and further from fan pulleys 302 and 306.As a result, fan belts 300 and 304 are drawn towards sheave shaft 214 soas to urge first and second movable sheave members 246 and 258,respectively towards corresponding outer sheave members 220 and 228,respectively, and into the low speed position, FIG. 12. As best seen inFIG. 12, the depths of fan belt receiving grooves 257 and 268 ofvariable pitch sheave assembly 212 are greater than the depths of drivebelt receiving grooves 255 and 270 of variable pitch sheave assembly212.

As generator structure 10 continues operation, the temperature of theengine coolant flowing through engine 124 and through radiator 132operatively connected thereto increases. Temperature sensor 294 sensesthe increased temperature of the engine coolant flowing through radiator132 and provides such information to controller 290 on line 296. As aresult, controller 290 retracts shaft 282 of actuator 284 such thatvariable pitch sheave assembly 212 moves towards the high speedposition, FIG. 13. As best seen in FIG. 11, as variable pitch sheaveassembly 212 moves towards the high speed position, variable pitchsheave assembly 212 is further from drive pulleys 204 and 206 and closerto fan pulleys 302 and 306. As such, drive belts 208 and 210 urge firstand second movable sheave members 246 and 258, respectively, away fromcorresponding outer sheave members 220 and 228, respectively, andtowards intermediate sheave member 236. It can be appreciated that thedepths of drive belt receiving grooves 255 and 270 in variable pitchsheave assembly 212 increase as first and second movable sheave members246 and 258, respectively, move from the low speed position, FIG. 12, tothe high speed position, FIG. 13. Further, with first and second movablesheave members 246 and 248, respectively, in the high speed position,FIG. 13, the depths of fan belt receiving grooves 257 and 268 is reducedsuch that the depths of the drive belt receiving grooves 255 and 270 isgreater than the depths of fan belt receiving grooves 257 and 268.

It can be appreciated that in the low speed position, drive belts 208and 210 travel along a greater circumferential path within drive beltreceiving grooves 255 and 270, respectively, variable pitch drive sheaveassembly 212 and fan belts 300 and 304 travel along a smallercircumferential path within fan belt receiving grooves 257 and 268 invariable pitch sheave assembly 212. Consequently, rotation of variablepitch sheave assembly 212 is translated to fan pulleys 302 and 306 suchthat fan 134 travels at a first predetermined speed. With variable pitchsheave assembly in the high speed position, FIG. 13, the path of drivebelts 208 and 210 circumferentially within drive belt receiving grooves255 and 270, respectively, in variable pitch sheave assembly 212 isreduced and the path of fan belts 300 and 304 circumferentially withinfan belt receiving grooves 257 and 268 in variable pitch sheave assembly212 is increased. As result, if drive pulleys 204 and 206 are rotated ata constant speed by jack shaft 150, the speed of rotation of variablepitch sheave assembly 212 will increase with the variable pitch sheaveassembly 212 in the high speed position, FIG. 13. In addition, in thehigh speed position, FIG. 13, fan belts 300 and 304 travel a greaterdistance for each revolution of variable pitch sheave assembly 212.Consequently, fan pulleys 302 and 306 will travel a greater distance foreach revolution of variable pitch sheave assembly 212, and as such,rotate fan 134 more quickly. As described, by repositioning variablepitch sheave assembly 212 from the low speed position, FIG. 12, to thehigh speed position, FIG. 13, the speed of rotation of fan 136 willincrease given a constant speed of rotation of jack shaft 150. Hence,fan 134 can draw or push more air through radiator 132 so as to enhancethe cooling effect thereof.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing anddistinctly claiming the subject matter which is regarded as theinvention.

We claim:
 1. A variable pitch drive sheave assembly for interconnectingfirst and second fan pulleys operatively connected to a fan by arotatable fan shaft and first and second rotatable drive pulleys, thefan generating an air flow through a radiator to cool the temperaturethereof, comprising: a shaft extending along an axis and having firstand second opposite ends; a first outer sheave member positionedadjacent the first end of the shaft; a second outer sheave memberpositioned adjacent the second end of the shaft; an intermediate sheavemember positioned between the first and second ends of the shaft; afirst movable sheave member slidable between the first outer sheavemember and the intermediate sheave member, the first movable sheavemember and the first outer sheave member defining a first drive pulleygroove therebetween for receiving a first drive belt and the firstmovable sheave member and the intermediate sheave member defining afirst fan pulley groove therebetween for receiving a first fan belt; asecond movable sheave member slidable between the second outer sheavemember and the intermediate sheave member, the second movable sheavemember and the second outer sheave member defining a second drive pulleygroove therebetween for receiving a second drive belt and the secondmovable sheave member and the intermediate sheave member defining asecond fan pulley groove therebetween for receiving a second fan belt;an actuator operatively connected to the shaft for moving the first andsecond movable sheave members between a first high speed position and asecond low speed position; a monitoring device for monitoring thetemperature of the radiator, the monitoring device controlling movementof the actuator in response to the temperature of the radiator; andwherein: the first drive belt operatively connects the first drivepulley groove and the first drive pulley; the second drive beltoperatively connects the second drive pulley groove and the second drivepulley; the first fan belt operatively connects the first fan pulleygroove and the first fan pulley; and the second fan belt operativelyconnects the second fan pulley groove and the second fan pulley suchthat rotation of the first and second drive pulleys is translated to thefirst and second fan pulleys.
 2. The drive sheave assembly of claim 1wherein the first and second drive pulley grooves have a first depthwith the first and second movable sheave members in the high speedposition and a second depth with the first and second movable sheavemembers in the low speed position.
 3. The drive sheave assembly of claim2 where the first depth of the first and second drive pulley grooves isgreater than the second depth of the first and second drive pulleygrooves.
 4. The drive sheave assembly of claim 1 wherein the first andsecond fan pulley grooves have a first depth with the first and secondmovable sheave members in the high speed position and a second depthwith the first and second movable sheave members in the low speedposition.
 5. The drive sheave assembly of claim 4 where the first depthof the first and second fan pulley grooves is less than the second depthof the first and second fan pulley grooves.
 6. A fan drive arrangementfor operatively connecting a drive shaft to a fan mounted on a rotatablefan shaft, the fan generating an air flow through a radiator to cool thetemperature thereof, comprising: first and second fan pulleysinterconnected to the fan shaft, each fan pulley having a groove thereinfor receiving a corresponding fan belt; first and second drive pulleysinterconnected to the drive shaft, each drive pulley having a groovetherein for receiving a corresponding drive belt; a variable pitchsheave assembly movable between a first high speed position and a secondlow speed position, the variable pitch sheave including: a rotatablesheave shaft having first and second opposite ends; a first outer memberfixed to the first end of the sheave shaft; a second outer member fixedto the second end of the sheave shaft; an intermediate member fixed tothe sheave shaft between the first and the second ends thereof; a firstslidable member slidable along the sheave shaft between the first outermember and the intermediate member; the first slidable member and thefirst outer member defining a first drive groove therebetween and thefirst slidable member and the intermediate member defining a first fangroove therebetween; a second slidable member slidable along the sheaveshaft between the intermediate member and the second outer member; thesecond slidable member and the second outer member defining a seconddrive groove therebetween and the second slidable member and theintermediate member defining a second fan groove therebetween; a firstdrive belt seated in the groove in the first drive pulley and the firstdrive groove to translate rotation of the first drive pulley to thevariable pitch sheave assembly; a second drive belt seated in the groovein the second drive pulley and the second drive groove to translaterotation of the second drive pulley to the variable pitch sheaveassembly; a first fan belt seated in the first fan groove and the groovein the first fan pulley to translate rotation of the variable pitchsheave assembly to the first fan pulley; a second fan belt seated in thesecond fan groove and the groove in the second fan pulley to translaterotation of the variable pitch sheave assembly to the second fan pulley;an actuator operatively connected to the variable pitch sheave assemblyfor moving the variable pitch sheave assembly between the high speedposition and the low speed position; and a controller operativelyconnected to the actuator and monitoring the temperature of theradiator, the controller controlling operation of the actuator inresponse to the temperature of the radiator.
 7. The fan drivearrangement of claim 6 wherein the first and second drive grooves have afirst depth with the variable pitch sheave assembly in the high speedposition and a second depth with the variable pitch sheave assembly inthe low speed position.
 8. The fan drive arrangement of claim 7 whereinthe first depth of the first and second drive grooves is greater thanthe second depth of the first and second drive grooves.
 9. The fan drivearrangement of claim 7 wherein the grooves in the first and second fanpulleys have a first depth with the variable pitch sheave assembly inthe high speed position and a second depth with the variable pitchsheave assembly in the low speed position.
 10. The fan drive arrangementof claim 9 wherein the first depth of the grooves in the first andsecond fan pulleys is less than the second depth of the grooves in thefirst and second fan pulleys.
 11. A fan drive arrangement foroperatively connecting a drive shaft to a fan mounted on a rotatable fanshaft, the fan generating an air flow through a radiator having coolantthereon to cool the temperature thereof; comprising: first and secondfan pulleys interconnected to the fan shaft, each fan pulley having agroove therein for receiving a corresponding fan belt; first and seconddrive pulleys interconnected to the drive shaft, each drive pulleyhaving a groove therein for receiving a corresponding drive belt; avariable pitch sheave assembly movable between a first high speedposition and a second low speed position, the variable pitch sheaveincluding: first and second drive belt grooves, the drive belt grooveshaving a first depth with the variable pitch sheave assembly in the highspeed position and a second depth with the variable pitch sheaveassembly in the low speed position; and first and second fan beltgrooves, the fan belt grooves having a first depth with the variablepitch sheave assembly in the high speed position and a second depth withthe variable pitch sheave assembly in the low speed position; first andsecond drive belts seated in corresponding drive belt grooves in thevariable pitch sheave assembly and in corresponding grooves in the drivepulleys to translate rotation of the drive pulleys to the variable pitchsheave assembly; and first and second fan belts seated in correspondingfan belt grooves in the variable pitch sheave assembly and incorresponding grooves in the fan pulleys to translate rotation of thevariable pitch sheave assembly to the fan pulleys; an actuatoroperatively connected to the variable pitch sheave assembly for movingthe variable pitch sheave assembly between the high speed position andthe low speed position; and a controller operatively connected to theactuator and monitoring the temperature of the coolant, the controllercontrolling operation of the actuator in response to the temperature ofthe coolant.
 12. The fan drive arrangement of claim 11 wherein thevariable pitch sheave assembly includes: a rotatable sheave shaft havingfirst and second opposite ends; a first outer member fixed to the firstend of the sheave shaft; a second outer member fixed to the second endof the sheave shaft; an intermediate member fixed to the sheave shaftbetween the first and the second ends thereof; a first slidable memberslidable along the sheave shaft between the first outer member and theintermediate member; the first slidable member and the first outermember defining the first drive belt groove therebetween and the firstslidable member and the intermediate member defining the first fan beltgroove therebetween; and a second slidable member slidable along thesheave shaft between the intermediate member and the second outermember; the second slidable member and the second outer member defininga second drive groove therebetween and the second slidable member andthe intermediate member defining the second fan belt groovetherebetween.
 13. The fan drive arrangement of claim 11 wherein thefirst depth of the drive belt grooves is greater than the second depthof the drive belt grooves.
 14. The fan drive arrangement of claim 11wherein the first depth of the fan belt grooves is less than the seconddept of the fan belt grooves.